1 #!/usr/bin/env python 2 3 """ 4 Convert and optimise images for display in an Acorn Electron MODE 1 variant 5 with four colours per line but eight colours available for selection for each 6 line. 7 8 Copyright (C) 2015 Paul Boddie <paul@boddie.org.uk> 9 10 This program is free software; you can redistribute it and/or modify it under 11 the terms of the GNU General Public License as published by the Free Software 12 Foundation; either version 3 of the License, or (at your option) any later 13 version. 14 15 This program is distributed in the hope that it will be useful, but WITHOUT ANY 16 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A 17 PARTICULAR PURPOSE. See the GNU General Public License for more details. 18 19 You should have received a copy of the GNU General Public License along 20 with this program. If not, see <http://www.gnu.org/licenses/>. 21 """ 22 23 from random import random, randrange 24 from os.path import split, splitext 25 import EXIF 26 import PIL.Image 27 import itertools 28 import math 29 import sys 30 31 corners = [ 32 (0, 0, 0), (255, 0, 0), (0, 255, 0), (255, 255, 0), 33 (0, 0, 255), (255, 0, 255), (0, 255, 255), (255, 255, 255) 34 ] 35 36 # Basic colour operations. 37 38 def extra(x): return x 39 40 def within(v, lower, upper): 41 return min(max(v, lower), upper) 42 43 def clip(v): 44 return within(v, 0, 255) 45 46 def distance(rgb1, rgb2): 47 r1, g1, b1 = rgb1 48 r2, g2, b2 = rgb2 49 return math.sqrt(pow(r1 - r2, 2) + pow(g1 - g2, 2) + pow(b1 - b2, 2)) 50 51 def restore(srgb): 52 return tuple(map(lambda x: int(x * 255.0), srgb)) 53 54 def scale(rgb): 55 return tuple(map(lambda x: x / 255.0, rgb)) 56 57 def square(srgb): 58 return tuple(map(lambda x: pow(x, 2), srgb)) 59 60 def invert(srgb): 61 return tuple(map(lambda x: 1.0 - x, srgb)) 62 63 # Colour distribution functions. 64 65 def combination(rgb): 66 67 "Return the colour distribution for 'rgb'." 68 69 # Get the colour with components scaled from 0 to 1, plus the inverted 70 # component values. 71 72 rgb = extra(scale(rgb)) 73 rgbi = invert(rgb) 74 pairs = zip(rgbi, rgb) 75 76 # For each corner of the colour cube (primary and secondary colours plus 77 # black and white), calculate the corner value's contribution to the 78 # input colour. 79 80 d = [] 81 for corner in corners: 82 rs, gs, bs = scale(corner) 83 84 # Obtain inverted channel values where corner channels are low; 85 # obtain original channel values where corner channels are high. 86 87 d.append((pairs[0][int(rs)] * pairs[1][int(gs)] * pairs[2][int(bs)], corner)) 88 89 # Balance the corner contributions. 90 91 return balance(d) 92 93 def complements(rgb): 94 95 "Return 'rgb' and its complement." 96 97 r, g, b = rgb 98 return rgb, restore(invert(scale(rgb))) 99 100 def balance(d): 101 102 """ 103 Balance distribution 'd', cancelling opposing values and their complements 104 and replacing their common contributions with black and white contributions. 105 """ 106 107 d = dict([(value, f) for f, value in d]) 108 for primary, secondary in map(complements, [(0, 0, 0), (255, 0, 0), (0, 255, 0), (0, 0, 255)]): 109 common = min(d[primary], d[secondary]) 110 d[primary] -= common 111 d[secondary] -= common 112 return [(f, value) for value, f in d.items()] 113 114 def combine(d): 115 116 "Combine distribution 'd' to get a colour value." 117 118 out = [0, 0, 0] 119 for v, rgb in d: 120 out[0] += v * rgb[0] 121 out[1] += v * rgb[1] 122 out[2] += v * rgb[2] 123 return out 124 125 def pattern(rgb, chosen=None): 126 127 """ 128 Obtain a sorted colour distribution for 'rgb', optionally limited to any 129 specified 'chosen' colours. 130 """ 131 132 l = [(f, value) for f, value in combination(rgb) if not chosen or value in chosen] 133 l.sort(reverse=True) 134 return l 135 136 def get_value(rgb, chosen=None, fail=False): 137 138 """ 139 Get an output colour for 'rgb', optionally limited to any specified 'chosen' 140 colours. If 'fail' is set to a true value, return None if the colour cannot 141 be expressed using any of the chosen colours. 142 """ 143 144 l = pattern(rgb, chosen) 145 limit = sum([f for f, c in l]) 146 if not limit: 147 if fail: 148 return None 149 else: 150 return l[randrange(0, len(l))][1] 151 152 choose = random() * limit 153 threshold = 0 154 for f, c in l: 155 threshold += f 156 if choose < threshold: 157 return c 158 return c 159 160 # Colour processing operations. 161 162 def sign(x): 163 return x >= 0 and 1 or -1 164 165 def saturate_rgb(rgb, exp): 166 return tuple([saturate_value(x, exp) for x in rgb]) 167 168 def saturate_value(x, exp): 169 return int(127.5 + sign(x - 127.5) * 127.5 * pow(abs(x - 127.5) / 127.5, exp)) 170 171 def amplify_rgb(rgb, exp): 172 return tuple([amplify_value(x, exp) for x in rgb]) 173 174 def amplify_value(x, exp): 175 return int(pow(x / 255.0, exp) * 255.0) 176 177 # Image operations. 178 179 def get_colours(im, y): 180 181 "Get a colour distribution from image 'im' for the row 'y'." 182 183 width, height = im.size 184 c = {} 185 for x in range(0, width): 186 rgb = im.getpixel((x, y)) 187 188 # Sum the colour probabilities. 189 190 for f, value in combination(rgb): 191 if not c.has_key(value): 192 c[value] = f 193 else: 194 c[value] += f 195 196 c = [(n/width, value) for value, n in c.items()] 197 c.sort(reverse=True) 198 return c 199 200 def get_combinations(c, n): 201 202 """ 203 Get combinations of colours from 'c' of size 'n' in decreasing order of 204 probability. 205 """ 206 207 all = [] 208 for l in itertools.combinations(c, n): 209 total = 0 210 for f, value in l: 211 total += f 212 all.append((total, l)) 213 all.sort(reverse=True) 214 return [l for total, l in all] 215 216 def test(): 217 218 "Generate slices of the colour cube." 219 220 size = 512 221 for r in (0, 63, 127, 191, 255): 222 im = PIL.Image.new("RGB", (size, size)) 223 for g in range(0, size): 224 for b in range(0, size): 225 value = get_value((r, (g * 256) / size, (b * 256 / size))) 226 im.putpixel((g, b), value) 227 im.save("rgb%d.png" % r) 228 229 def test_flat(rgb): 230 231 "Generate a flat image for the colour 'rgb'." 232 233 size = 64 234 im = PIL.Image.new("RGB", (size, size)) 235 for y in range(0, size): 236 for x in range(0, size): 237 im.putpixel((x, y), get_value(rgb)) 238 im.save("rgb%02d%02d%02d.png" % rgb) 239 240 def rotate_and_scale(exif, im, width, height, rotate): 241 242 """ 243 Using the given 'exif' information, rotate and scale image 'im' given the 244 indicated 'width' and 'height' constraints and any explicit 'rotate' 245 indication. The returned image will be within the given 'width' and 246 'height', filling either or both, and preserve its original aspect ratio. 247 """ 248 249 if rotate or exif and exif["Image Orientation"].values == [6L]: 250 im = im.rotate(270) 251 252 w, h = im.size 253 if w > h: 254 height = (width * h) / w 255 else: 256 width = (height * w) / h 257 258 return im.resize((width, height)) 259 260 def count_colours(im, colours): 261 262 """ 263 Count colours on each row of image 'im', returning a tuple indicating the 264 first row with more than the given number of 'colours' together with the 265 found colours; otherwise returning None. 266 """ 267 268 width, height = im.size 269 for y in range(0, height): 270 l = set() 271 for x in range(0, width): 272 l.add(im.getpixel((x, y))) 273 if len(l) > colours: 274 return (y, l) 275 return None 276 277 # Main program. 278 279 if __name__ == "__main__": 280 281 # Test options. 282 283 if "--test" in sys.argv: 284 test() 285 sys.exit(0) 286 elif "--test-flat" in sys.argv: 287 test_flat((120, 40, 60)) 288 sys.exit(0) 289 elif "--help" in sys.argv: 290 print >>sys.stderr, """\ 291 Usage: %s <input filename> <output filename> [ <options> ] 292 293 Options are... 294 295 -s - Saturate the input image (can be repeated) 296 -d - Desaturate the input image (can be repeated) 297 -D - Darken the input image (can be repeated) 298 -B - Brighten the input image (can be repeated) 299 -2 - Square/diminish the bright corner colour contributions (experimental) 300 301 -r - Rotate the input image clockwise 302 -p - Generate a separate preview image 303 -h - Make the preview image with half horizontal resolution (MODE 2) 304 -v - Verify the output image (loaded if -n is given) 305 -n - Generate no output image 306 """ % split(sys.argv[0])[1] 307 sys.exit(1) 308 309 width = 320 310 height = 256 311 312 input_filename, output_filename = sys.argv[1:3] 313 basename, ext = splitext(output_filename) 314 preview_filename = "".join([basename + "_preview", ext]) 315 316 options = sys.argv[3:] 317 318 # Preprocessing options that can be repeated for extra effect. 319 320 saturate = options.count("-s") 321 desaturate = options.count("-d") 322 darken = options.count("-D") 323 brighten = options.count("-B") 324 325 # Experimental colour distribution modification. 326 327 use_square = "-2" in options 328 if use_square: 329 extra = square 330 331 # General output options. 332 333 rotate = "-r" in options 334 preview = "-p" in options 335 half_resolution_preview = "-h" in options 336 verify = "-v" in options 337 no_normal_output = "-n" in options 338 make_image = not no_normal_output 339 340 # Load the input image if requested. 341 342 if make_image or preview: 343 exif = EXIF.process_file(open(input_filename)) 344 im = PIL.Image.open(input_filename).convert("RGB") 345 im = rotate_and_scale(exif, im, width, height, rotate) 346 347 width, height = im.size 348 349 if saturate or desaturate or darken or brighten: 350 for y in range(0, height): 351 for x in range(0, width): 352 rgb = im.getpixel((x, y)) 353 if saturate or desaturate: 354 rgb = saturate_rgb(rgb, saturate and math.pow(0.5, saturate) or math.pow(2, desaturate)) 355 if darken or brighten: 356 rgb = amplify_rgb(rgb, brighten and math.pow(0.5, brighten) or math.pow(2, darken)) 357 im.putpixel((x, y), rgb) 358 359 # Generate a preview if requested. 360 361 if preview: 362 imp = im.copy() 363 step = half_resolution_preview and 2 or 1 364 for y in range(0, height): 365 for x in range(0, width, step): 366 rgb = imp.getpixel((x, y)) 367 value = get_value(rgb) 368 imp.putpixel((x, y), value) 369 if half_resolution_preview: 370 imp.putpixel((x+1, y), value) 371 372 imp.save(preview_filename) 373 374 # Generate an output image if requested. 375 376 if make_image: 377 for y in range(0, height): 378 c = get_colours(im, y) 379 380 for l in get_combinations(c, 4): 381 most = [value for f, value in l] 382 for x in range(0, width): 383 rgb = im.getpixel((x, y)) 384 value = get_value(rgb, most, True) 385 if value is None: 386 break # try next combination 387 else: 388 break # use this combination 389 else: 390 most = [value for f, value in c[:4]] # use the first four 391 392 for x in range(0, width): 393 rgb = im.getpixel((x, y)) 394 value = get_value(rgb, most) 395 im.putpixel((x, y), value) 396 397 if y < height - 1: 398 rgbn = im.getpixel((x, y+1)) 399 rgbn = tuple(map(lambda i: clip(i[0] + i[1] - i[2]), zip(rgbn, rgb, value))) 400 im.putpixel((x, y+1), rgbn) 401 402 im.save(output_filename) 403 404 # Verify the output image (which may be loaded) if requested. 405 406 if verify: 407 if no_normal_output: 408 im = PIL.Image.open(output_filename).convert("RGB") 409 410 result = count_colours(im, 4) 411 if result is not None: 412 y, colours = result 413 print "Image %s: row %d has the following colours: %s" % (output_filename, y, "; ".join([repr(c) for c in colours])) 414 415 # vim: tabstop=4 expandtab shiftwidth=4